But the colonel said that it was vital that the deaths did not "drive a wedge" between the Afghan police and his men who would continue to take the fight to the Taliban.

Sgt Maj Darren Chat, 39, Sgt Matthew Telford, 39, Guardsman James Major, 18, together with Royal Military Police Corporals Steven Boote, 22, and Nicholas Webster, 24, all died last Tuesday after being shot dead inside an Afghan Police Compound known as Blue 25. A further six were injured in the attack.

Col Walker said the killing of his regimental sergeant major had left the unit bereft of its finest soldier but added that morale within his unit remained high.

"Sergeant Major Darren 'Daz' Chant was the living embodiment of the professional soldier," Col. Walker said.

"He died with his boots on. If he could have chosen the way he had to die on operations – that would have been it, on the ground, working with soldiers, doing the job he loved."

He added: "We will remember them all and we will mourn them properly when we return to the UK but right now we have to continue with the mission – the Sgt Maj would not have wanted it any other way."

The attack occurred on Tuesday in the village of Shin Kalay in the Nad e'Ali area of central Helmand, which up until last year was a Taliban stronghold, and remains one of the most dangerous areas of Helmand.

In a moving interview with The Sunday Telegraph, Col Walker, 39, described the moment he learned that five members of his battle group had been murdered as "just chilling" and added that it was a "desperate blow" for the battalion.

The tragedy unfolded as the colonel was about to return to his headquarters in Nad e'Ali after visiting another police station. A message came over the radio announcing that Blue 25 was under attack.

He continued: "It took two or three seconds to sink in and I thought dam – that's my team. We were told that it was under attack and I felt well if it's under attack, I know the position, its fortified the boys will be in it, the sergeant major will be all over it – I'm happy.

"I was almost inclined to say 'okay fine, no matter, give me an update when it's over'. Then we were told that it was serious and that there were casualties. We immediately headed off (towards Blue 25) and then it came over the radio that there were ISAF (International Security and Assistance Force) dead, which is just chilling when you hear that as a commanding officer.

"It trickled in that there were three dead and that it was a mass casualty situation, which sounded horrific. Then we were told that there were four dead and the remainder were seriously injured and the evacuation was taking place. At that point your heart just sank. We were only five kilometres away but on these roads, with the threat of improvised explosive devices, that is around 45 mins to an hour away.

"So we made our way down and going through your mind is the worst – you're asking yourself "who's dead?". I knew there were four dead and I knew that they had been shot from the inside the base. I went straight to the headquarters because we were told the dead and wounded had been evacuated.

"I was met by the senior major who told me that the sergeant major was dead. It was a desperate blow but, by that stage I had kind of expected that to be the case. And then he explained that Sergeant Telford had been killed, a very gentle man, and that one of the [Royal Military Police] Corporals had been killed and that Guardsman Major had been killed.

"He had just joined us and was going to be 19 in a couple of day's time and this was his first tour. Then later, some time after, I learned that the second RMP Corporal had died.

"It was a treacherous act, it was monstrous. This was a man the Sgt Maj had helped train and they were killed then when they were unarmed and off their guard.

"So you take a pause, you take a breath, and realise you have got to take control of the situation and deal with the living."

Col Walker went down to the regimental aid post and visited the casualties, one of whom was unconscious and on a ventilator and who had been shot twice. Another Guardsman had been shot in the hand.

While the Colonel was visiting the injured troops, those Guardsmen who had been unhurt in the attack arrived at the headquarters.

He added: "As you can imagine they were in a state of shock, some were very emotional, very upset at what had happened and the enormity of what they had seen had sunk in."

The colonel said that it was not until the following days that the loss really began to hit home.

Col Walker, who was originally commissioned into the Irish Guards, had come to rely heavily upon Sgt Major Chant, whom he described as "my conscience, my right hand man".

He went on: "From the first day that I took over command of the battalion through to the day the Sgt Maj died I would consult him on every significant decision concerning soldiers or the regiment.

"The tragedy is that as I was going through the formalities of writing up notes on the incident my instinct was to turn to the Sgt Maj and say 'right, what do we do about this?'. But obviously he's not there and that's when you realise you are on your own at that point.

"I missed him very, very quickly and I still do but for the battlegroup he was a really big personality and this will come out in the telling as people remember him.

"He has left us a great legacy, every word he said will be remembered, Yes, he was a living legend but my God now he is preserved."

Sgt Maj Chant had been sent to help train and "mentor" the Afghan National Police unit located in Shin Kalay, which had been heavily infiltrated by the Taliban.

The colonel said the task had been both difficult and dangerous but one to which Sgt Maj Chant and his team of 14 soldiers were uniquely suited.

Col Walker, who is married with three children, continued: "He was coming to the end of his time with the Afghan Police. I kept trying to pull him out but he wanted to stay, that was the kind of man he was. He loved the job and he had the Afghan Police eating out of his hand.

"They saluted him every day and called him Mr Daz. He was due to come back to the main headquarters in the week that he was killed."

While the killing of the five soldiers had raised questions about the future of the Afghan mission back home in Britain, Colonel Walker said that his men were determined to succeed in Helmand.

Colonel Walker said that it was vital that the attack did not drive a wedge between the British Army and the Afghan security forces.

He said that one of the Taliban's key propaganda messages was that NATO forces were an Army of occupation because they often conducted operations on their own.

He said: "Where we operate with the sons of Afghanistan and where we are working hand in hand with them, it absolutely counters the Taliban message. So it's really important that the general public see us working together because it gives them the confidence that we are sensitive to local culture. And my soldiers understand this absolutely so we will continue to work alongside the Afghans – it is non-negotiable, there is no other way to carry out this operation and win over the locals without working hand in glove with our partners."

Colonel Walker added that he believed that Afghan police were "terribly brave" men who lived in the knowledge that one in ten of their number would die fighting the Taliban.

He said: "If we were to allow any wedges to form between us they (the ANP) would wither and they would fall prey to the Taliban. So I have

said to the boys "it's no change". We have to be guarded, we have to anticipate reverses like this but to my mind this is a one-off."

The hunt for the killer is now being largely conducted by the Afghan Interior Ministry and being headed by a Brigadier General. The Afghan Intelligences services are also involved, while a separate investigation is being conducted by the Special Investigation Branch of the Royal Military Police.

The troops' role in Nad e'Ali, the area where Colonel Rupert Thorneloe, the commanding officer of the Welsh Guards was operating when he was killed in July, is to create localized security zones for the local Afghan population.

In theory such safe havens will be protected by an outer cordon of British troops allowing the local population to lead relatively normal lives free from Taliban attack and intimidation.

As a consequence of such a strategy, British troops are now being attacked every day. In the last month alone Colonel Walker's 1000 strong battle group has reported more than 200 shooting attacks and discovered 107 suspected IEDs.

He continued: "Life is very busy. The boys are active on all fronts. We have contacts (attacks) every day – it is everything we expected. It is full-spectrum counter insurgency.

"We have got communities with localized security where the Afghans are on the inside and we are on the outside. The schools are opening, the roads are improving, wells are being dug and people are coming back so there is a lot of engagement.

"We have weekly Shuras where most of the elders will come in and talk about the problems of the day and we work out how we can help.

"What we are trying to do is to push ourselves away from the population centers so that when the fighting happens it happens to us and by doing that we keep the Taliban away from the people and we are doing that with the Afghan Army.

"On the inside of these protected communities we are working alongside the Afghan police who are basically providing community policing; who are making sure the bazaars are safe and who are cutting down on crime. But the Taliban are still present although they are not coming in bearing arms they are trying to intimidate and influence."

The plan is ultimately to link up the various secure areas by road which should in time allow the communities to flourish and commerce to prosper. But for that to happen the Afghans must have the confidence to be able to repel the influence of the Taliban.

Col Walker continued: "The Afghan people are stuck between what we are offering and what the Taliban are trying to do. There is no BBC or Sky

TV out there, there are no newspapers so everything is done by word of mouth and it is very easy for the Taliban to misrepresent what we are trying to do. A lot of these locals don't know any better ad they will believe what they are told. So the idea is to get our message across through the ANA and the ANP to the village elders.

In the meantime British soldiers will continue to endure. Casualties in Helmand are a daily occurrence, flags in British bases more often fly at half masts than not and calls for emergency blood donors are becoming increasingly regular.

But despite the losses there is no great sense amongst British troops in Helmand that the mission has reached a "tipping point". Despite the deaths suffered by the battalion, the Grenadier Guards have now lost four soldiers since they arrived in October, Col Walker said morale remains high.

He added: "The companies have not skipped a beat. They continue to be in action and the troops remain focused. I would say that the resolve and the morale of the battlegroup remains as strong as it ever was. There is a time and a place for us to remember Sgt Maj Chat, Sgt Telford, Guardsman Major and Guardsman James but we will do that when we get home.

"For now we will deal with the incident and we get on with the job in hand and we live up to the expectations of those who have made the ultimate sacrifice."